Cutting inserts made of hard wear resistant material, such as a cemented hard metal carbide, perform very adequately when removing metal from a workpiece. Because of the feeds and speeds utilized in removing metal from a workpiece when using a cemented hard metal carbide insert, safety, efficiency and workpiece finish require that the metal removed from the workpiece be broken into discrete individual chips that may be conveniently collected and removed from the work area.
Chipbreakers take many forms and, in some cases, may be a separate structure that is used in conjunction with a cutting insert or the chipbreaker may take the form of a groove integrally molded in the cutting insert.
The metal being removed from the workpiece by the cutting insert is sheared from the parent metal in a region near the cutting edge of the insert being used. As the metal slides over the cutting insert and to the rear of the cutting edge, a chipbreaking obstruction, such as the integrally molded groove mentioned above, impedes the free flow of the sheared metal and deflects or bends the sheared metal in order to break it into discrete individual chips of a manageable size.
When such a chipbreaker plate or groove impedes or bends the sheared metal so as to break it into chips, additional work is done to the chip other than the work required to shear the metal from the parent workpiece. This additional work requires greater power consumption, thereby generating greater temperatures on the cutting edge and face of the insert.
Chipbreakers of the prior art, when used with a positive rake insert, have usually put too much work into the act of bending the sheared metal by presenting unnecessarily severe obstructions in the path of the metal being removed from the workpiece. When this is done, greater conditions of temperature and force are put on the cutting edge of the insert, ultimately leading to premature failure of the cutting edge of the insert.
It has been found, with the geometry of the present invention, that the obstruction to the path of the metal being removed from the workpiece can be minimized and still provide for efficient breakage of the chips over a wide range of feeds and speeds.